1. Field of the Invention
The present invention relates to a circuit arrangement for a communications system for the transmission of serial bit message information, particularly of multiplex data transmitted within optical transmission systems, via local networks having loop configurations and equipped with corresponding switching devices, a plurality of terminal equipment processing different types of information being connectible to the local network in arbitrary combination with one another, the plurality of terminal equipment being adapted to the different types of communication in view of quantity of data transmission and the data transmission rate within a frame, as well as in view of the method of transmission.
2. Description of the Prior Art
A communications system of the general type set forth above is known from the German published application No. 33 04 823 in which different subscriber terminal equipment which can exchange messages with one another are connected to a light waveguide network configured as a loop. The exchange of the messages thereby occurs without the involvement of a centrally-provided exchange controller and can optionally occur with the assistance of a continuous transmission method and/or of a packet transmission method. What is referred to as the hybrid method in which a synchronously-circulating pulse frame is divided into two sub-frames, the so-called stream frame and burst frame, within the loop network is utilized for designational transmission of the data between the terminal equipment. The first of these sub-frames is thereby composed of (m-1) time slots (time channels) and serves for the transmission of continuous signals such as, for example, digitized signals having data rates of, for example, 64 kbit/s per time slot. The second sub-frame is not subdivided and can be operated, for example, with a data rate of 4.096 Mbit/s. The second sub-frame serves, first of all, for the signaling of the channels of the first subframe, for example for call setup and call cleardown, and also serves for fast data exchange between modern office equipment which must send or, respectively, receive greater quantity of data in bursts at certain times. The second sub-frame is operated in accordance with what is referred to as the token method.
Since, based on its very principle, the hybrid method is not limited in data rate, a data rate far higher than, for example, 8 Mbit/s can also be used in such a loop network.
Under the precondition that moving picture communication, i.e. picture telephone, picture monitoring, picture conferencing, etc, is also to be transmitted in future "integrated" communications networks, the picture information must be digitized, as is the other voice and data information.
It is known for connecting the individual broadband terminal equipment, to connect the same to a centrally-disposed broadband switching matrix arrangement and to through-connect the corresponding routes via the switching matrix network for the duration of the transmission. An individual line group comprising, for example, a picture channel plus a few narrow band channels which are likewise switched via the central exchange therefore leads to every such broadband subscriber. Under the assumption that the broadband channel can be based on a data rate of 34 Mbit/s and a further 4 Mbit/s rate can be used for the narrow band channels, a data rate of about 38 Mbit/s derives on the forward line or, respectively, on the return line of the communications system. Since both the broadband communications and the narrow band connections must be through-connected via the centrally-controlled switching system, no fast data communication can be achieved within such a communications system due to the lacking bus structure despite the existing, high data rates because of the times for the call setup or, respectively, call cleardown are too high due to the centralization.
If, on the other hand, data were to be transmitted simultaneously on a single loop-shaped line over a plurality of broadband channels having data rates of 34 Mbit/s per channel in accordance with the known method (hybrid method), then a sum data rate of k.times.34 Mbit/s i.e. 340 Mbit/s for k=10 channels, would derive here plus the data rate of the narrow band channel (burst subchannel) of, for example, 4 Mbit/s.
Such data rates, however, cannot be economically governed at present or in the foreseeable future with the presently-available optical and electronic switching components.